Low resistance ground joints for dual stage actuation disk drive suspensions

ABSTRACT

A stainless steel dual stage actuated disk drive head suspension baseplate including a plated electrical contact area having nickel and gold. The baseplate can be heat treated. The nickel and gold can be in a mixture.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/531,571, filed on Nov. 3, 2014, which is a continuation of U.S.patent application Ser. No. 13/114,212, filed May 24, 2011, now U.S.Pat. No. 8,885,299, issued Nov. 11, 2014, which claims the benefit under35 U.S.C. 119 of Provisional Application No. 61/396,239, filed May 24,2010, which are incorporated herein by reference in their entirety forall purposes.

TECHNICAL FIELD

The present invention relates to suspensions for disk drives. Inparticular, the invention is a dual stage actuation (DSA) suspension andmethod of manufacture.

BACKGROUND OF THE INVENTION

Dual stage actuation (DSA) disk drive head suspensions are generallyknown and commercially available. By way of example, one embodiment of aDSA head suspension 10 is shown in FIGS. 1A and 1B. The illustrated DSAsuspension includes a baseplate 12, hinge 14 or spring region, load beam16 and integrated lead flexure 18 with traces 20. The hinge 14 ismounted to the baseplate 12 and extends from the distal end of thebaseplate. The load beam is mounted to the distal end of the hinge 14.The flexure 18 is mounted to the load beam 16, typically on the side ofthe load beam mounted to the hinge 14. Welds such as 22 are typicallyused to join these components. The baseplate 12, hinge 14 and load beam16 are typically formed from stainless steel, and the flexure 18typically includes a base layer of stainless steel. The copper or copperalloy traces 20 on the flexure 18 are separated from the stainless steelbase layer by a layer of polyimide or other insulator.

The second stage actuation functionality of the illustrated DSAsuspension 10 is incorporated into the baseplate 12. As shown, thebaseplate 12 has one or more motor-receiving areas or openings 24 (twoin the illustrated embodiment). Piezoelectric (PZT) motors 26 aremounted to the baseplate 12 in the motor-receiving openings 24. Themotors 26 are mounted to tabs 28 extending from the baseplate 12 intothe motor-receiving openings 24. In the illustrated suspension 10 thetabs 28 are portions of the hinge 14. In other embodiments (not shown)the tabs 28 to which the PZT motors 26 are mounted can be othercomponents such as a separate motor plate welded to the baseplate. Epoxyor other adhesive is typically used to mount the motors 26 to the tabs28.

DSA suspensions can be embodied in still other forms. For example, analternative DSA suspension structure is illustrated and described in theOkawara U.S. Patent Publication No. 2010/0067151 which is incorporatedherein by reference in its entirety and for all purposes. Briefly, thesuspension shown in the Okawara publication has an actuator plate towhich the motors are mounted. The actuator plate is mounted between thebaseplate and hinge. In still other DSA suspensions (not shown), themotors can be mounted to the load beam or hinge.

An electrical connection or conductive joint between an electricalground contact on a face of the motor and the ground plane of thesuspension is typically made by conductive adhesive (e.g., epoxy withsilver and/or nickel particles). The ground contacts on the motorstypically have an external plated gold (Au) layer. These connections aretypically formed by applying a mass of the conductive adhesive at alocation where the ground contact of the motor is adjacent to astainless steel portion of the baseplate, load beam, hinge or flexure.The conductive adhesive contacts both the motor ground contact and thestainless steel portion of the suspension, thereby providing anelectrical connection or ground joint from the motor to the stainlesssteel portions of the suspension that function as the ground plane.

The conductive joint between the motor and the ground plane should becapable of functioning at or below a threshold level of acceptableresistance under all applied processing and operational load conditions.However, consistently maintaining acceptable resistance to ground levelshas been difficult. In particular, the resistance of the conductiveadhesive-to-stainless steel component joints have been determined to berelatively high and unstable.

SUMMARY OF THE INVENTION

Embodiments of the invention include a stainless steel disk drive headsuspension baseplate including a plated contact area. The plated contactarea comprises nickel and gold. In embodiments, the plated contact areacomprises a mixture of nickel and gold. The baseplate and contact areaare heat treated in embodiments. The baseplate is a dual stage actuatedbaseplate in embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an isometric illustration of the flexure side of a prior artdual stage actuation (DSA) suspension.

FIG. 1B is an isometric illustration of the opposite, baseplate side ofthe prior art suspension shown in FIG. 1A.

FIG. 2 is a plan view illustration of a portion of a DSA suspension inaccordance with an embodiment of the invention having a plated flexure.

FIG. 3 is a plan view illustration of an alternative embodiment of thesuspension shown in FIG. 2.

FIG. 4 is a side view illustration of a portion of a DSA suspension inaccordance with another embodiment of the invention having a platedflexure.

FIG. 5 is a plan view illustration of the suspension shown in FIG. 4.

FIG. 6 is a plan view illustration of a portion of a DSA suspension inaccordance with another embodiment of the invention having a formedflexure tab.

FIG. 7 is a side view illustration of the suspension shown in FIG. 6.

FIGS. 8 and 9 are plan view illustrations of portions of a DSAsuspension in accordance with another embodiment of the invention havinga plated hinge.

FIGS. 10 and 11 are plan view illustrations of portions of a DSAsuspension in accordance with another embodiment of the invention havinga plated hinge having a tab. The tab is shown unformed in FIG. 10 andformed in FIG. 11.

FIG. 12 is an isometric illustration of the suspension shown in FIG. 11.

FIGS. 13 and 14 are plan view illustrations of portions of a DSAsuspension in accordance with another embodiment of the invention havinga plated add-on feature.

FIG. 15 is a plan view illustration of a plated unformed baseplate inaccordance with another embodiment of the invention.

FIG. 16 is a plan view illustration of the plated baseplate in FIG. 15in the formed state.

FIG. 17 is a plan view illustration of a portion of a DSA suspension inaccordance with an embodiment of the invention having a plated plug.

FIG. 18 is a plan view illustration of the baseplate and plated plugcomponents of the suspension shown in FIG. 17.

FIG. 19 is a cross section side view illustration of the assembledbaseplate and plated plug components shown in FIGS. 17 and 18.

DETAILED DESCRIPTION Overview

The invention is a dual stage actuation (DSA) suspension having astable, low resistance conductive adhesive electrical connection orjoint between an electrical contact on a motor of the suspension and aplated metal contact area on a stainless steel component of thesuspension. One embodiment of the invention includes a ground jointbetween the electrical contact of a piezoelectric (PZT) motor and a goldor nickel gold plated contact area on the stainless steel suspensioncomponent. The gold or nickel gold or other conductive and generallynon-corrosive metal or alloy plated area on the stainless steelsuspension component is referred to generally in the description of theinvention below as the plated region. In still other embodiments a layerof nickel is plated on the stainless steel, and a gold layer is platedon the nickel layer.

As described below in connection with the attached drawing figures, theinvention can be embodied in a number of different structures. Forexample, the invention can be embodied in DSA suspensions such as thatdescribed above in connection with FIGS. 1A and 1B. Alternatively, theinvention can be embodied in DSA suspension structures of the typedisclosed in the Okawara U.S. Patent Publication No. 2010/0067151. Forexample, the stainless steel suspension component to which the groundjoint is made can be a baseplate, load beam, hinge, motor plate, flexureor other component. The plated contact area on the stainless steelsuspension component can be heat treat annealed. In some embodiments ofthe invention, the plated contact surface retains a full surfacecoverage of the plated alloy. In other embodiments of the invention theplated contact surface includes approximately 98% stainless steel and 2%gold following the heat treat and annealing process. In yet otherembodiments, the plated contact surface includes about 90% stainlesssteel surface and about 10% gold. Only the portion of the component towhich the conductive adhesive ground joint is being made need be plated(e.g., patterned and selectively plated), although in other embodimentslarger areas or even the entire component surface can be plated.

The invention provides a reliable, stable and low resistance jointbetween the conductive adhesive and the plated stainless steel contactarea. The desired resistance level can vary with the application of thesuspension (e.g., with the drive circuitry that the motor is to beconnected). One example specification calls for ground contactresistance levels no greater than 2500 ohms. Another specification callsfor resistance levels no greater than 100 ohms. Still other embodimentsof the invention have a resistance no greater than 10 ohms and even lessthan 1 ohm over the life of the suspension.

Plated Flexure Embodiments

FIGS. 2 illustrates portions of a suspension 110 in accordance with anembodiment of the invention having a through hole or opening 130 in thebaseplate 112 that exposes a gold plated contact 132 on the flexure 118.Features of the suspension 110 that are similar to those of suspension10 described above in connection with FIGS. 1A and 1B are identified bysimilar reference numbers in the “100” series. Conductive adhesive 134extends from the motor contact 136, over the baseplate 112, into andthrough the baseplate opening 130, and to the plated flexure contact132. The plated contact 132 on the flexure 118 can be a contact plateddirectly onto the stainless steel base layer of the flexure 118. In analternative embodiment shown in FIG. 3 illustrating portions ofsuspension 110′ a through hole 131′ is etched or otherwise formedthrough the stainless steel base layer of the flexure 118′ to expose aplated portion of a trace 120′ on the flexure. In this alternativeembodiment the conductive adhesive 134′ extend through the holes 130′and 131′ in the baseplate 112′ and the flexure 118′, and contacts theplated flexure trace 120′.

FIGS. 4 and 5 illustrate portions of a suspension 210 in accordance withanother embodiment of the invention. Features of the suspension 210 thatare similar to those of suspension 10 described above in connection withFIGS. 1A and 1B are identified by similar reference numbers in the “200”series. In this embodiment the mass of conductive adhesive 234 extendsfrom the motor contact 236, over the edge of the motor 226, into a gap227 between the motor and baseplate 212, and into contact with theplated contact region 232 on the flexure 218. As with the embodimentshown in FIGS. 2 and 3, the plated contact 232 on the flexure 218 can beon the stainless steel base layer or on a trace exposed at a throughhole (not shown) in the flexure. Non-conductive adhesive 233 is used tomount the motor 226 to the hinge tabs 228 and isolate the second(bottom) electrode of the motor from the conductive adhesive 234 of theground joint.

Formed Flexure Embodiments

FIGS. 6 and 7 illustrate portions of a suspension 310 in accordance withanother embodiment of the invention having a flexure 318 with a tab 360or paddle on the stainless steel base layer 361 that has a platedcontact 362. Features of the suspension 310 that are similar to those ofsuspension 10 described above in connection with FIGS. 1A and 1B areidentified by similar reference numbers in the “300” series. The flexuretab 360 is formed (e.g., two 90° bends 363, 364 are shown) to extend outof the plane of the other portions of the flexure 318, through a gap 365between the baseplate 312 and motor 324, and into contact with theground contact 336 on the motor. A mass of conductive adhesive 334 joinsthe plated contact 362 on the formed flexure tab 360 to the motor groundcontact 336.

Plated Hinge Embodiments

FIGS. 8 and 9 illustrate portions of a suspension 410 in accordance withanother embodiment of the invention having a plated contact 470 on aportion of the hinge near or adjacent to the motor 426 (e.g., the hingemotor tab). FIG. 9 shows the suspension 410 after a de-tabbing steprelative to FIG. 8. Features of the suspension 410 that are similar tothose of suspension 10 described above in connection with FIGS. 1A and1B are identified by similar reference numbers in the “400” series. Theconductive adhesive 434 extends from the motor contact 436 over the edgeof the motor 426 and into contact with the plated contact 470 on thehinge 414. In the illustrated embodiments the conductive adhesive 434also extends over a portion of the baseplate 412 and the edge of thebaseplate.

FIGS. 10-12 illustrate portions of suspension 510 in accordance withanother embodiment of the invention having a formed plated hinge 514.Features of the suspension 510 that are similar to those of suspension10 described above in connection with FIGS. 1A and 1B are identified bysimilar reference numbers in the “500” series. A plated contact 570 isformed on a tab 580 extending from the hinge 514. The tab 580 is shownin an unformed state in FIG. 10. During suspension 510 assembly the tab580 is formed to extend up the edge and over the baseplate 512 at alocation adjacent to the motor 526. The conductive adhesive 534 extendsbetween the motor ground contact 536 and the plated contact 570 on theformed tab 580, across the baseplate 512.

Add-On Feature Embodiments

FIGS. 13 and 14 illustrate portions of a suspension 610 in accordancewith another embodiment of the invention including a separatelymanufactured plated element or feature 682 that is welded (e.g., bywelds 622) or otherwise attached to the baseplate 612 adjacent to themotors 626. The conductive adhesive 634 extends from the motor contactpad 636 to the plated surface 681 of the feature 682, over the edge ofthe feature. FIG. 14 shows the suspension 610 after a de-tabbing stepand application of conductive adhesive 634 relative to FIG. 13.

Plated Baseplate Embodiments

FIGS. 15 and 16 illustrate plated baseplates 712 in accordance withanother embodiment of the invention. A plated stripe 790 is formed onthe baseplate stock. FIG. 15 shows the baseplate 712 unformed. The stockis formed with the plated stripe 790 located adjacent to the motoropenings 724 as shown in FIG. 16. The mass of conductive adhesive (notshown) will extend between the motor contact (not shown) and the platedportion 790 of the baseplate 712.

Plated Plug Baseplate

FIGS. 17-19 illustrate portions of a suspension 810 in accordance withanother embodiment of the invention including plated stainless steelplugs 892 in the baseplate 812. Features of the suspension 810 that aresimilar to those of suspension 10 described above in connection withFIGS. 1A and 1B are identified by similar reference numbers in the “800”series. The plated plugs 892 can be manufactured separately from thebaseplate 812, and mechanically forced into holes in the baseplate withthe plated surface 893 oriented toward the same side of the baseplate asthe motor contacts 836. The plug 892 can be press fit, coined orotherwise forced into the hole in the baseplate 812 to form asubstantial and secure mechanical, and low resistance contact betweenthe plug and baseplate. Coining provides the additional adavantage ofleaving a depression that can be useful in adhesive wicking control.FIG. 19 is a cross section view of an assembled baseplate 812 and platedplug 892. The conductive adhesive 834 is applied so that it extendsbetween the plated surface 893 of the plug 892 and the motor groundcontact 836.

Although the invention is described with reference to a number ofdifferent embodiments, those skilled in the art will recognize thatchanges can be made in form and detail without departing from the spiritand scope of the invention.

The following is claimed:
 1. A stainless steel disk drive headsuspension baseplate including a plated contact area, wherein the platedcontact area comprises nickel and gold.
 2. The baseplate of claim 1wherein the plated contact area comprises a mixture of nickel and gold.3. The baseplate of claim 2 wherein the baseplate and contact area areheat treated.
 4. The baseplate of claim 3 wherein the contact areaincludes gold in an amount of about 2%-10%.
 5. The baseplate of claim 3wherein the baseplate is a dual stage actuation baseplate that includesa first portion having a swage mount and a T-shaped portion having astem extending from the first portion, and wherein the contact areaincludes a portion on the first portion of the baseplate adjacent theT-shaped portion.
 6. The baseplate of claim 5 wherein the portion of thecontact area on the first portion of the baseplate is shaped as astripe.
 7. The baseplate of claim 5 wherein the plated contact area islocated on only a portion of the baseplate.
 8. The baseplate of claim 5wherein the contact area includes portion on the stem of the T-shapedportion.
 9. The baseplate of claim 5 wherein the contact area includesgold in an amount of about 2%-10%.
 10. The baseplate of claim 2 whereinthe contact area includes gold in an amount of about 2%-10%.
 11. Thebaseplate of claim 1 wherein the contact area includes gold in an amountof about 2%-10%.
 12. The baseplate of claim 1 wherein the contact areais shaped as a stripe.
 13. The baseplate of claim 1 wherein baseplate isa dual stage actuation baseplate that includes a first portion having aswage mount and a T-shaped portion having a stem extending from thefirst portion, and wherein the contact area includes a portion on thefirst portion of the baseplate adjacent the T-shaped portion.
 14. Thebaseplate of claim 13 wherein the portion of the contact area on thefirst portion of the baseplate is shaped as a stripe.
 15. The baseplateof claim 13 wherein the plated contact area is located on only a portionof the baseplate.
 16. The baseplate of claim 13 wherein the contact areaincludes portion on the stem of the T-shaped portion.
 17. A method formanufacturing a disk drive head suspension baseplate, including:applying nickel and gold to a contact area of a stainless steelbaseplate; and heat treating the baseplate after applying the nickel andgold.
 18. The method of claim 17, including applying amounts of nickeland gold to the stainless steel baseplate and heating the baseplate toproduce a contact area having about 2%-10% gold.
 19. The method of claim17 wherein applying nickel and gold includes: applying a layer ofmaterial including nickel on the stainless steel baseplate; and applyinga layer of gold on the layer of material including nickel.